Significance of information obtained during transanal drainage tube placement after anterior resection of colorectal cancer

Introduction It has recently been reported that the placement of a transanal drainage tube after rectal cancer surgery reduces the rate of anastomotic leakage. However, transanal drainage tube cannot completely prevent anastomotic leakage and the management of transanal drainage tube needs to devise. We investigated the information obtained during transanal drainage tube placement and evaluated the relationship between these factors and anastomotic leakage. Patients and methods Fifty-one patients who underwent anterior resection of rectal cancer was retrospectively reviewed. transanal drainage tube was placed for more than 5 days after surgery. The daily fecal volume from transanal drainage tube was measured on postoperative day 1–5, and the defecation during transanal drainage tube placement was investigated. Results Anastomotic leakage during transanal drainage tube placement occurred in 4 patients. The anastomotic leakage rate during transanal drainage tube placement in patients whose maximum daily fecal volume or total fecal volume from the transanal drainage tube during postoperative days 1–5 was large was significantly higher than that in patients whose fecal volume was small. The anastomotic leakage rate of the patients with intentional defecation during transanal drainage tube placement was significantly higher than that of the patients without intentional defecation during transanal drainage tube placement. The maximum daily fecal volume and the total fecal volume from the transanal drainage tube during postoperative days 1–5 in patients who experienced intentional defecation during transanal drainage tube placement was significantly higher than that of patients without intentional defecation during transanal drainage tube placement. Conclusion A large fecal volume from transanal drainage tube after anterior rectal resection or intentional defecation in patients with transanal drainage tube placement were suggested to be risk factors for anastomotic leakage.


Introduction
It has recently been reported that the placement of a transanal drainage tube after rectal cancer surgery reduces the rate of anastomotic leakage. However, transanal drainage tube cannot completely prevent anastomotic leakage and the management of transanal drainage tube needs to devise. We investigated the information obtained during transanal drainage tube placement and evaluated the relationship between these factors and anastomotic leakage.

Patients and Methods
Fifty-one patients who underwent anterior resection of rectal cancer was retrospectively reviewed. transanal drainage tube was placed for more than 5 days after surgery. The daily fecal volume from transanal drainage tube was measured on postoperative day 1-5, and the defecation during transanal drainage tube placement was investigated.

Results
Anastomotic leakage during transanal drainage tube placement occurred in 4 patients. The anastomotic leakage rate during transanal drainage tube placement of patients whose maximum daily fecal volume or total fecal volume from the transanal drainage tube during postoperative day 1-5 was large was significantly higher than that in patients whose fecal volume was small. The anastomotic leakage rate of the patients with intentional defecation during transanal drainage tube placement was significantly higher than that of the patients without intentional defecation during transanal drainage tube placement. The maximum daily fecal volume and the total fecal volume from the transanal drainage tube during postoperative day 1-5 in patients who experienced intentional defecation during transanal drainage tube placement was significantly higher than that of patients without intentional defecation during transanal drainage tube placement.

Conclusion
A large fecal volume from transanal drainage tube after anterior rectal resection or intentional defecation in patients with transanal drainage tube placement were suggested to be risk factors for anastomotic leakage.  2 The authors declare that they have no competing interests in regard to this study. during transanal drainage tube placement of patients whose maximum daily fecal volume 13 or total fecal volume from the transanal drainage tube during postoperative day 1-5 was 14 large was significantly higher than that in patients whose fecal volume was small. The Anastomotic leakage after the resection of colorectal cancer is a serious complication 2 that is associated with short-term outcomes, such as reoperation, extension of hospital 3 stay, and increased perioperative mortality [1-5], as well as long-term oncological effects, 4 such as a poor prognosis due to local recurrence [6][7][8]. The anastomotic leakage rate after 5 resection of rectal cancer is higher in comparison to other colon cancers [9]. Thus, in 6 order to prevent anastomotic leakage after low-anterior resection (LAR) of the rectum, 7 various methods have been adapted, such as adequate mobilization of the colon [10], the 8 use of intracorporeal reinforcing sutures [11] and evaluation of the blood flow by 9 fluorescence imaging with indocyanine green (ICG) [12]. In addition, in cases in which 10 there is considered to be a high risk of anastomotic leakage, such as cases with 11 anastomosis at a low rectal position, diverting stomas can be constructed to reduce the 12 burden of anastomosis [13]. Recently, it has been reported that the placement of a transanal 13 drainage tube (TDT), which is technically easy and which can economically decompress 14 the anastomotic site [14], is effective for preventing anastomotic leakage after rectal 15 cancer surgery [15][16][17]. However, even if a TDT is used, defecation may occur that does 16 not pass through the TDT, and anastomotic leakage may occur. Furthermore, the timing 17 of the removal of the TDT was sometimes delayed based on the judgment of each surgeon.

18
Thus, there may be room for improving the method of managing TDT in the perioperative 1 period. The present study therefore explored the mechanism underlying the occurrence of 2 anastomotic leakage despite using a TDT by evaluating the association between the 3 perioperative clinical information obtained during TDT placement and anastomotic 4 leakage and suggested a strategy for preventing anastomotic leakage. Thus, we 5 retrospectively evaluated the association between clinical information during TDT 6 placement and anastomotic leakage.   The daily fecal volume from TDT and the total fecal volume for the 5 days of TDT 7 placement (PODs 1-5 after the resection for CRC) were measured.

8
The cut-off values of the fecal volume were calculated based on an ROC curve analysis 9 in order to determine the relationship between anastomotic leakage and the fecal volume 10 from the TDT. The patients were divided to two groups: the high volume group and the 11 low volume group. 12 The fecal matter that did not pass through the TDT during POD 1-5 was investigated 13 from electronic medical records. In this study, the defecation that patients consciously 14 performed during TDT placement was defined as intentional defecation, while the 15 discharge that flowed outside the TDT unconsciously was defined as fecal incontinence. 16 We evaluated the associations between anastomotic leakage and intentional defecation 17 and between anastomotic leakage and fecal incontinence.

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In addition, a subgroup analysis of patients in whom no anastomotic leakage occurred 1 during TDT placement was performed. The association between the fecal volume from 2 the TDT at POD 5, when TDT removal was scheduled, and the anastomotic leakage after 3 removal of TDT was evaluated.

4
The details of anastomotic leakage were collected from the medical records of each 5 surgeon. Anastomotic leakage was defined by major leakage (e.g., fecal discharge from 6 the abdominal drain tube or the discharging of contrast agent into the abdominal cavity 7 during fluoroscopic examination) and by minor leakage (e.g., free air around the 8 anastomotic site on CT after the patient presented fever or abdominal pain).

9
All of the statistical analyses were performed using JMP 14.2.0 (SAS Institute, Japan, 10 Tokyo). The chi-squared test, the Fisher's exact test and Mann-Whitney U-test were used 11 to analyze the significance of associations between 2 groups. P values of <0.05 were 12 considered to indicate statistical significance. 13 This retrospective study was approved by the Ethics Committee of Osaka City 14 University (approval number: 4182) and conducted in accordance with the Declaration of 15 Helsinki. All patients provided their written informed consent.  Preoperative factors associated with anastomotic leakage. 3 We used the tumor diameter, which was a continuous variable, as the test variable and 4 the occurrence of anastomotic leakage as the state variable. When we investigated the 5 cut-off value for the tumor diameter using the ROC curve, we found that the appropriate The anastomotic leakage rate was significantly higher in the groups with LAR and 10 ≥35.0 mm tumor diameter than in the other groups (p=0.016, p=0.006, respectively) 11 (    for the maximum daily fecal volume from the TDT during PODs 1-5 using the ROC curve, 5 we found that the appropriate cut-off value for the maximum daily fecal volume was  The anastomotic leakage rate during TDT placement in patients in whom the maximum 12 daily fecal volume from the TDT during POD 1-5 was ≥100.0 ml was significantly higher 13 than that of the patients in whom the maximum daily fecal volume from the TDT during 14 POD 1-5 was <100.0 ml (p=0.007). The anastomotic leakage rate during TDT placement 15 in patients in whom the total fecal volume from the TDT during POD 1-5 was ≥260.0 ml 16 was significantly higher than that of the patients in whom the total fecal volume from the 17 Association between fecal discharge not through TDT and the 6 anastomotic leakage during TDT placement. 7 The anastomotic leakage rate of the patients who experienced fecal incontinence during 8 TDT placement was not significantly different from that in patients without fecal 9 incontinence during TDT placement. However, the anastomotic leakage rate of patients 10 who experienced intentional defecation during TDT placement was significantly higher 11 than that of patients without intentional defecation during TDT placement (p=0.028) 12 (Table 4). The maximum fecal volume from the TDT during POD 1-5 in patients who 9 experienced intentional defecation during TDT placement was significantly higher than 1 that of patients without intentional defecation during TDT placement (p=0.026) (Fig 1a). 2 The total fecal volume from the TDT during POD 1-5 in patients who experienced 3 intentional defecation during TDT placement was significantly higher than that of patients 4 without intentional defecation during TDT placement (p=0.010) (Fig 1b).

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The total fecal volume from the TDT during POD 1-5 in patients in whom the tumor 18 diameter was ≥35.0 mm tended to be higher than that of the patients in whom the tumor 1 diameter was <35.0 mm (p=0.051) ( Table 5).
2 The subgroup analysis of the anastomotic leakage that 7 occurred after TDT removal, among the patients who did not 1 develop anastomotic leakage during TDT placement. 2 Among the 47 patients who did not develop anastomotic leakage during TDT 3 placement, 4 patients developed anastomotic leakage after removal of the TDT. 4 We used the daily fecal volume from the TDT on POD 5, which was a continuous 5 variable, as the test variable and the occurrence of anastomotic leakage after removal of 6 the TDT as the state variable. When we investigated the cut-off value for the daily fecal 7 volume from the TDT on POD 5 using the ROC curve, we found that the appropriate cut-8 off value for the daily fecal volume from the TDT on POD 5 was 80.0 ml (sensitivity of 9 50.0%; specificity of 86.0%) (S3 Fig). We therefore set this fecal volume as the cut-off 10 value and classified patients into high and low groups.

11
The anastomotic leakage rate after removal of the TDT of patients for whom the daily 12 fecal volume from the TDT on POD 5 was ≥80.0 ml tended to be higher in comparison 13 to the patients for whom the daily fecal volume from the TDT on POD 5 was <80.0 ml 14 (p=0.067) ( Table 6).
15 Table 6 In the subgroup of 47 patients in whom no anastomotic leakage occurred of patients in whom the daily fecal volume from the TDT after laparoscopic LAR 18 exceeded 100 ml/day for two or more days was significantly higher than that of those in 1 whom the daily fecal volume from the TDT did not exceed 100 ml/day or in whom it only 2 exceeded this cut-off value for one day [20]. In our study, it was similarly revealed that 3 an increased fecal volume from the TDT was significantly associated with an increased 4 rate of anastomotic leakage. Thus, the fecal volume from the TDT is considered to be 5 useful for predicting anastomotic leakage. 6 Our study revealed that intentional defecation during TDT placement was significantly 7 associated with an increased anastomotic leakage rate, and patients with intentional 8 defecation during TDT placement have a significantly greater total fecal volume in the 5 9 days after surgery. Given these results, one of the mechanisms underlying ruptured 10 anastomoses during TDT placement was suggested to be due to a large volume of watery 11 stool that occurred after the operation, thus leading to poor drainage from the rectum and 12 intentional defecation and eventually resulting in too much compression occurring at the 13 site of anastomosis.
14 In addition, a larger tumor diameter was considered to be a risk factor for an increased Thus, the appropriate management of TDT is important for decompression to prevent 2 anastomotic leakage during TDT placement. We should not only avoid bending the 3 drainage tube to prevent obstruction but also devise a bowel preparation to prevent severe 4 watery diarrhea after surgery. In particular, the present study suggested that appropriate 5 bowel preparation was necessary for patients with a large tumor diameter. 6 In addition, intentional defecation during TDT placement was considered associated 7 with a high risk of anastomotic leakage. In cases in which intentional defecation is 8 observed, TDT management should be strictly performed. On the other hand, there was 9 no association between fecal incontinence and anastomotic leakage. Thus, fecal 10 incontinence was considered to reflect good drainage of the rectum and was not associated 11 with a need for increased vigilance. 12 In the present study, some patients developed anastomotic leakage after the removal of 13 the TDT. These patients developed anastomotic leakage after POD 5, likely due to 14 postoperative factors, such as watery diarrhea. In these cases, the TDT was removed 15 despite drainage by the TDT still being necessary, so frequent defecation occurred after 16 its removal, and anastomotic leakage then developed due to the physical compression of 17 the anastomotic site. Thus, in cases involving a high fecal volume on POD 5, it was 18 suggested that treating the watery diarrhea and delaying the removal of the TDT or the 1 start of meal intake might help prevent anastomotic leakage after the removal of the TDT. 2 The present study was associated with some limitations. First, this study was a 3 retrospective study that included a relatively small number of patients who were managed 4 at a single institution. Second, the method of bowel preparation and the criteria for 5 removal of the TDT were not uniform and they depended on the choice of each surgeon. 6 Thus, a prospective study should be performed after establishing appropriate criteria, such 7 as the methods of bowel preparation or the timing of removal of the TDT.      The receiver operating characteristic curve of the diameter of tumor for anastomotic leakage is shown.